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hello my name is colin and this episode
of let's learn blender we'll be talking
about two of blender's 3d modeling tools
first the knife tool the knife tool is
used to let you create custom edges in
pretty much any direction on any face of
the surface of a mesh that you want it's
a super powerful tool and the second
tool we're talking about is called the
bicep tool which lets you cut clean
through a mesh and what that means that
you're cutting basically a loop around
your mesh wherever you want and you can
even adjust where it is and the angle
that cut through the mesh is facing and
you can even use the bisect tool to
remove or chop off part of a mesh and
even cut a mesh into two with a few
extra steps so we'll be talking about
these two tools in this video this will
be a little bit of a shorter video in
this series we'll go ahead and put on
the bottom of the screen right now how
you can help me out by clicking like
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you've not checked out the rest of this
video series on youtube this is my
tutorial series called let's learn
blender i'll put a link to this whole
series up on the top of the screen right
now so go ahead and check that out so
diving into the knife tool in blender
the knife tool is a tool that you access
while you're in edit mode of a 3d mesh
object in blender so of course with a
mesh object selected you press tab to
switch from object mode into edit mode
the knife tool is one of the tools along
your side toolbar i'll go ahead and drag
the edge of my toolbar to make it a
little bit wider so i can see all the
tools on the screen now the knife tool
is right here and if i select it you
will notice that my mouse cursor if i go
ahead and zoom in
is now a little picture of a knife and
all i have to do here is click anywhere
on the surface of my mesh object in edit
mode to start creating a cut in other
words an edge that starts with a vertex
and runs to another vertex now there are
a few things to keep in mind here if you
create a cut on the surface or an edge
on the surface of a mesh an edge can't
just end in the middle of a face so i'm
gonna go ahead and click just on an edge
and it'll kind of snap if i'm not exact
to that edge and you can see when i
click it creates a green square which is
a vertex and i can move my mouse i'm not
holding anything down right now and i
can simply click on another edge and
that creates the beginning of a cut and
now i could keep going but i'm going to
go ahead and make that edge that cut
permanent simply by pressing the enter
key on my keyboard
when i do that now of course if i switch
over to my select tool and i'll go into
face selection mode i can select either
of those two faces and i can do whatever
i want with them let's say i could
select this face and press the e key on
my keyboard to extrude i can move my
mouse and click of course the e key on
my keyboard is the extrude tool and so
now i have an extruded face right there
now you don't just have to make one cut
from edge to edge the knife tool is a
lot more powerful than that if i go
ahead to this other side i'll orbit and
pan over so you can see this side a
little bit better if i use the
knife tool again and start on the same
kind of upper edge i can make a zigzag
pattern creating new vertices along my
cut in the middle of a face so i'm going
to click down on this edge usually go
from edge to edge typically so i'm going
to click and you can see i can keep
going with this cut or of course i can
press the enter key on my keyboard or
the return key and that completes that
cut and so now if i go to the selection
tool and i go to face select mode and i
select either one of these faces they
are in fact faces now they are n-gone
faces that means they are faces with
more than three or four sides but
they're still faces in facelike mode i
could tap the e key and extrude and yeah
you can see i've got a pretty silly
looking extrusion or face here extruded
out
it is important to note that when you're
using the knife tool you cannot simply
cut a hole in the surface of a face so
if i want to create let's say a square
hole in the middle top of my cube i
could cut from there to there i'm just
clicking now with my knife tool and i
can complete this cut you can see that
if i press the enter key on my keyboard
it doesn't just let me create a face in
the middle of another large face you
can't do that in blender so it
automatically created connections or
connecting edges from my middle face out
to a couple of corners just based on
what it thought would be best for the
faces on the top of my cube so you can't
just have a face in the middle of
another face
something else you can do with a knife
tool is you can create new separate cuts
before you press enter to finalize the
cuts that you've just made let's go and
see what i mean if i go back to my knife
tool and i create a cut from this corner
if you just click it'll snap to that
corner or to that vertex and i click on
this vertex well maybe i want to cut
from there to there but then i want to
let's say create another cut from here
to here before i press enter on my
keyboard to make those two cuts
permanent i can simply do that by
pressing the letter e on my keyboard i'm
not sure why it's letter e it just is
but when you press e it kind of
finalizes that cut and now i can orbit
around and create a new cut here to
there in fact i'm going to press e on my
keyboard again and i'm going to create a
cut from oh let's say that bottom corner
down here up to there and i'll tap e and
start from here and go to there and now
if i press the enter key on my keyboard
all of those cuts that i just made are
finalized so now i could go ahead to my
selection tool and i could select let's
say that face and that face and tap e to
extrude them out and maybe i could
select this face and this face and tap e
to extrude them out and i could select
this face and tap e and extrude it in so
there's a fairly interesting geometric
3d shape that we've created fairly
quickly using different options in the
knife tool now the knife tool has of
course this active tool here on your
toolbar but if you just want to have
your selection tool enabled and quickly
get to the knife tool the legacy
keyboard shortcut in blender is the
letter k on your keyboard k is for knife
and the reason i'm showing you this is
because the legacy k version of the
knife tool has a few more options and
they are listed on the bottom
information bar at the bottom of
blender's interface so you can see down
here i'll go ahead and zoom in that if
you press the enter key on your keyboard
it confirms a cut if you press the
escape key or right mouse button it
cancels your current cut with the knife
tool if you press the left mouse button
it defines or starts a cut if you double
tap the left mouse button it closes the
cut the e key as we've covered before
makes a new cut while you're still using
the knife tool here's a new one it's the
control key and the control key if you
hold it down
it turns on mid point snap and if you
let go of the control key on your
keyboard it turns off midpoint snap what
does that mean well i'm going to go
ahead and press the ctrl key on my
keyboard and hover over the edges of
this cube in edit mode you can see it
snaps no matter where i have my mouse
cursor
a point to the middle of that edge so
i'm going to go ahead and click there
i'm going to keep holding ctrl and i'll
click there and then i'll press enter on
my keyboard and you can see i've cut the
top face of this cube perfectly in half
let's go ahead and press the k key again
to keep going through those little
keyboard shortcuts the control key of
course is midpoint snap the shift key
will ignore snap so if you want to
create a new point or a vertex near an
edge you see how when i move my mouse
cursor it snaps to an edge well if i
don't want that if i want to make a
point that's right near an edge i can
simply hold the shift key on my keyboard
and now it won't snap to an edge so i
can create you know a cut that's very
near an edge and i can press enter of
course it's not going to let me put an
edge in the middle of the face so it
connected both of my ends up to the
nearest corners okay pressing k again to
go through the rest of those keyboard
shortcuts c is the angle constraint
keyboard shortcut so if i press the
letter c on my keyboard well i've turned
angle constraint on so if i start making
a cut you can see i'll just click off to
the side that it's constraining my cuts
to 45 degree angles and these angles are
based on my current view in my 3d
viewport so because i'm looking at my
scene from a random user perspective
view it's going to cut and if i cut all
the way across my mesh yes you can start
off the mesh and go across and click
it's going to cut at 45 degrees based on
my view and i can press enter and if i
orbit my scene you can see well now it's
no longer at 45 degrees compared to my
view but it was just a moment ago so if
you're going to use the angle constraint
option you might want to go to a top or
front or side or bottom view to look at
your scene first before you start making
that cut of course you can use your
number pad keys on your keyboard or i
could press this little minus y uh
button on my little gizmo axis up here
to go to my front orthographic view if
you're not in orthographic you can press
this button right here it toggles
between perspective and orthographic
orthographic means flat and so now if i
press the letter k key on my keyboard
and then i tap the c key to turn on
angle constraint now i can cut directly
across
and press enter and i know that edge is
flat with my ground because i use angle
constraint the last keyboard shortcut is
really powerful it lets me cut all the
way through my mesh it's letter z on my
keyboard if i tap k to go into my knife
tool you can see the z key is called cut
through if i tap z i can now cut
through my mesh
and press enter and you can see if i
orbit around it actually cut all the way
through my mesh including
faces that i couldn't see before from
that angle and so now i have a cut a
loop cut essentially all the way through
my mesh by the way if you want to do
that with the active knife tool here
that option is called occlude geometry
it's turned on by default so you don't
cut through
all the way through a mesh it only cuts
the faces you can see
so it ends right there
and right there the color i just made
i'm going to go ahead and undo that if i
have occluded geometry turned off and i
cut all the way through and i press
enter well you can see now it goes all
the way around based on the view or
angle of my view that i was at just a
moment ago
this knife tools cut through option
along with the angle constraint option
can be a real life saver if you ever run
into a problem where you're trying to do
a loop cut through a mesh or around a
mesh object and you can't because of
n-gons let me show you what i mean if i
go ahead and press the letter k on my
keyboard to go into my knife tool and
i'm going to hold the ctrl key on my
keyboard and make a cut across the top
of this cube from the middle over here
with the control key to the middle over
here i'll go ahead and press enter i'm
going to turn my little cube into a very
simple little
house now if i want to later add a door
to the front of my house here well i'm
probably going to want to extrude a door
inward a rectangle inward so i might
want to make a loop cut around my house
so that i'm forming the top edge of my
door so if i go ahead and press ctrl r
on my keyboard control r brings up my
loop cut and slide tool you can see i
can hover my mouse over the mesh and you
can see from some directions of this
loop cut tool it goes all the way around
the mesh like it should
but in some directions it doesn't and
that's because i'll go ahead and press
escape on my keyboard that's because i
have a face here and a face here that
are n-gons they are faces with more than
four sides you can see
one two three four five
so this face kind of interrupts
loop cuts because when you make a loop
cut around a mesh it needs to know the
exact opposing edge to start at and to
go to and if i make a loop cut from
there to there well it doesn't know on
this face if this cut here should go
from that point over to this point or up
to this point because there's no
immediate opposing edge at least as far
as it's concerned so how do i make a
loop cut around my house well i could
use the knife tool i'll go back and
press escape i'll go back to my
selection tool i'll press letter k on my
keyboard i want to make a cut that goes
across my house perfectly flat so
actually i'm going to go to my front
view i'm going to press the little minus
y button up here actually i'll go to my
side view so i'll press the letter x
here now i'm in my right orthographic
view what i want to do here is i want to
make a cut all the way through my house
but straight across perfectly so i'm
going to press letter k to use my knife
tool i'm going to turn on angle
constraint with letter c of tap c so
it's on i'm going to turn on cut through
as well so i'll tap z on my keyboard so
now angle constraint and cut through are
both on and so now if i click over here
i can then move my house across and
click over here and now if i press enter
on my keyboard and zoom out and orbit
around you can see it's made a loop cut
essentially all the way around my house
and i could use my selection tool in
edge select mode and i could select i'll
hold alt on my keyboard and click on an
edge there to select the entire edge
loop alt and click select an edge loop
on edge and so now i can use the move
tool and move that edge loop down to
wherever i want the top of the roof to
be so as you can see the knife tool can
be a great problem solving tool
especially when you want blender to make
a topology that means an organization of
faces and edges on the surface of a mesh
that it's not giving you by default so
that's the knife tool the second tool
i'll be showing you in this video is
called the bisect tool and the bisect
tool is actually a tool on your toolbar
i'll go ahead with this uv sphere
selected and i'll make my toolbar a
little bit wider so we can see all the
tools it's actually hiding behind the
knife tool here so if i click and hold
on the knife tool icon
and i hold you can see i have the knife
tool and the bisect tool and you can
tell if i let go on it
that it looks like a tool you can use to
chop off part of a mesh and that's
pretty much what it is except it's a bit
more powerful than that so let's go
ahead and check out how you use it for
this i'm using a uv sphere just to mix
things up a little bit if i use the
bisect tool what i want to do here is
start off the edge of the mesh and click
and drag across the mesh and if i keep
holding down i can adjust where the mesh
will be cut
across so if i move my mouse around and
then i let go it's made a cut not just
across my mesh where i can see it's
actually made a loop cut essentially
around my mesh wherever i defined it and
it's giving me this funny looking little
gizmo this gizmo on my screen by the way
a gizmo is basically any control and
blender on your screen lets you move
where that cut is now if you go down to
this little pop over you can see under
the bisect pop over that you can adjust
its plane so where it is you can adjust
kind of
its location you can adjust its normal
the plane normal which is basically its
rotation in any of the three
axes like that you can select clear
inner or clear outer clear outer
basically gets rid of the mesh
that is where this gizmo arrow is
pointing and you can select clear inner
which will get rid of below where that
surface of the arrow is pointing if you
select one of the clear outers or clear
inners and also select fill i'll select
clear outer and fill it will make the
new
face of the cut into a solid face an end
gone in this case so now you can see
i've used this tool the bicep tool to
cut off part of the mesh now you're
probably thinking to yourself hey
couldn't you just do this with a knife
tool
yes you probably could
but probably in a few more steps than
with the bisect tool so this just makes
it a little bit easier to do well this
process with a knife tool of course you
could make a cut across the mesh you
could make that cut cut through all the
way through the mesh and then you could
delete part of the mesh and you could
fill in the gap on the new side of the
mesh but this just makes it much quicker
with this bicep tool though you can also
cut a mesh into two separate meshes with
a few extra steps so i'll go ahead and
do that i'll press ctrl z on my keyboard
to get rid of that bisect cut and i'll
use my bisect tool by the way if you
don't want to use this active tool you
can go up to the mesh menu and it is
right here i believe there is no
keyboard shortcut for it though like the
k key for the knife bisect doesn't have
that so if i select the bisect tool it
works the same way i can click and drag
and i can let go
and because i already had used this tool
and set these two options it did those
for me automatically of course i could
adjust you know where
the normal is i could adjust
the angle
of it i believe
in some way i believe it starts your cut
up here so it bases the rotation of the
plane normal uh up here instead of in
the middle of your cut or mesh object
that's okay but what i'm going to do
here instead of clearing either the
inner or the outer i'm just going to
fill in and create a face uh in the
middle of that new edge loop that's cut
all the way through my mesh
and now i'm going to actually select one
half or the other so i'm going to go up
to the select menu i still have that new
edge loop selected i'll go up to the
select menu and i'm going to go to
select loops
under select loops i'm going to select
select loop inner region and what i have
to do before i do anything else you can
see i was expecting it to select either
one half or the other i actually have to
select down here select bigger and it'll
select the i guess it's the bigger half
of your mesh object if you want to
separate the other half of the mesh you
could always go up to select and invert
that's up to you i'm going to select
invert again to select that original
bigger half and now if i want to
separate this mesh or this part of the
mesh into a separate mesh to create two
halves where i use my bisect tool i can
press letter p on my keyboard p brings
up the separate menu and i can simply
separate the selection here so i'll
click on selection and now i have a
separate mesh object for my bottom half
i'm still in edit mode of the top half
so i'll press tab on my keyboard or use
the mode menu so now i have a mesh
object there i'll go ahead and press g
on my keyboard and click to move it up
and i have a mesh object here so two
separate mesh objects now because i use
that fill option with my bisect tool you
can see the bottom half in my case has
that filled big n gone face there if i
press tab to go into this mesh object's
edit mode there is in fact an n-gone
here if i press tab and orbit around you
can see
there's a gap or a hole in the mesh
there is no filled side there that's a
pretty easy fix i'm gonna go ahead and
just grab that and move a little bit
farther away if i press tab to go into
edit mode of this top mesh and i use the
edge select tool and i hold the alt key
on my keyboard and click on one of the
edges around the hole you can see hey is
selected well in my case all of the
edges around the hole and i can simply
press the letter f on my keyboard to
create a new face or to fill
around those edges or in those edges
okay so that's the f key to fill and
i'll press tab to go back into object
mode and now i have two halves of cut
through my mesh now one last thing is of
course that i have these origins these
little orange dots here and on this mesh
object here and usually origins are in
the middle of a mesh unless you specify
them to be somewhere else in my case i
want to move these origins the middle of
the mesh because when you use one of the
transform tools the move rotate or scale
tools
the little handles for those tools
gizmos they will be coming off of that
origin so this looks a little bit weird
it really should be in the middle of the
mesh so i'm going to select that mesh go
up to the object menu and set origin
to geometry and that will put that
little orange dot in the middle of that
selected mesh's geometry so if i click
on that you can see it jumps up to right
there and now my gizmo handles a little
bit easier to understand i'll select
this one
object
set origin to geometry
there we go so now i have two mesh
objects out of one using the bisect tool
so that will be it for this video if you
made it to this point in this video
thank you so much for watching again my
name is colin and of course if you like
this video or if you learned something
in it please go ahead and click on that
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except here on youtube of course but
that'll be it for this one thank you so
much again for watching i'll see the
next one bye
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you
![[2.93] Blender Tutorial: How to Cut Through Objects](https://i.ytimg.com/vi/9mw9tvtqOEI/mqdefault.jpg)
